In the United States, lung cancer is the most common cause of cancer-related death in both men and women and 80% of these lung cancer cases are non-small cell lung cancers (NSCLCs). Adenocarcinomas in particular account for 30% of NSCLC cases, and include a rising population of cancer cases that occur in nonsmokers. In patients with NSCLC, KRAS mutations at codons 12, 13, and 61 have been identified as tumorigenic. Jacks and Tuveson have created a mouse model of NSLC driven by the conditional expression of a single allele of the K-rasG12D mutation in the lung. In this model, the mutant K-rasG12D allele is transcribed from its endogenous promoter after the intratracheal administration of an adenovirus encoding Cre recombinase. Within weeks, the mice develop multifocal benign and malignant tumors in the lung, providing clear evidence that this mutation is sufficient to drive tumorigenesis. This system is ideal for studying endogenously produced, in vivo lung adenocarcinomas and provides a platform to study the mechanisms underlying oncogenic Ras driven lung tumorigenesis. We will utilize this mouse model to test whether Notch signaling in required for oncogenic Ras driven adenocarcinoma using gain and loss of function mutants of Notch. Notch family consists of four different notch receptors, referred to as Notch1-4. Notch is cleaved upon binding ligand binding by y-secretase resulting in an intracellular domain of Notch (Notch ICD) which translocates to the nucleus. All four Notch ICD's in the nucleus regulate gene transcription through its interaction with the RBP-J protein. Notch 1 has been previously implicated as a target of oncogenic Ras driven transformation. However, the role in lung cancer is not fully understood. We will test the hypothesis that Notch signaling is required for the growth of K-rasG12D driven tumors. Aim 1 will determine whether loss of Notch function attenuates K-ras G12D driven mouse lung tumorigenesis. Aim 2 will determine whether gain of Notch function cooperates with K-ras G12D driven mouse lung tumorigenesis. AIM3 will determine whether RBP-J mediated Notch transcriptional activity is required for the K-ras G12D driven mouse lung tumorigenesis. Currently there are available drugs that inhibit y-secretase thereby preventing cleavage of Notch and the release of Notch ICD. If the results of the current study demonstrate that Notch is required for oncogenic Ras driven lung adenocarcinoma then it would provide a rationale to test the efficacy of these y-secretase inhibitors in patients suffering from oncogenic Ras driven lung adenocarcinoma. PHS 416-1 (Rev. 9/08) Page 2 Number pages consecutively at the bottom throughout Form Page 2 the application. Do not use suffixes such as 2a, 2b. Kirschstein-NRSA Individual Fellowship Application NAME OF APPLICANT (Last, first, middle initial) Tormos, Kathryn V. (To be completed by applicant - follow PHS 416-1 instructions) 18.